How Big a Punch Will This Storm Pack?

This major winter storm is easy to identify in the eastern U.S. (Source: NOAA)

Residents of the Washington, D.C. – Baltimore region have hunkered down for the area’s largest snowstorm in at least six years.  Some may wonder how often significant snowfall occurs during an El Nino winter in this part of the country.  Although November and December were warmer than average in Washington, D.C., more winter-like weather has certainly returned this month. 

Our current storm has been anticipated for several days by meteorologists as the computer models have done a pretty remarkable job.  It’s unusual for the models to be as consistent as they have been so far in advance.  With just enough cold air in place and ample moisture for the storm to draw upon – from both the Atlantic Ocean and the Gulf of Mexico – historic snowfall is likely.  Storm totals of 18” to 24” are likely for the immediate DC-Baltimore corridor with higher amounts on the west side of town.  The last snowfall of this magnitude in the Nation’s Capital came roughly six years ago in February 2010. 

It’s interesting to note that a few of the top 10 snowfalls on record in both Washington, D.C. and Baltimore have occurred during episodes of El Nino.  The current El Nino is one of the strongest on record – comparable to the 1997-1998 and 1982-1983 El Nino events.  However, unlike the 1997-1998 winter season, Washingtonians experienced a major winter storm during the 1982-1983 winter. 

The storm total of 16.6” that occurred in Washington, D.C. on February 10-11, 1983, was the 4^th largest snowfall on record at the time.  That illustrates that major snowfall does sometimes occur in the Mid-Atlantic Region during a very strong El Nino.  More recently, the 2002-2003 and 2009-2010 winters had moderate intensity El Nino events, yet three of Washington’s top ten snowfalls occurred during those two winters.  The February 2010 “Snowmageddon” storm was the largest among them.  According to the National Weather Service, that storm is currently the 4^th largest snowstorm on record in the Nation’s Capital with a total of 17.8”.

Weather records in the Nation’s Capital are kept at National Airport and snowfall values there are typically lower than in areas north and west of the city.  With 18” to 24” of snow a good bet with this storm downtown (and amounts of 30” or more possible in areas north and west of downtown) that would put this storm fairly high on the top ten snowfall – potentially even among the top five largest snowstorms in Washington, D.C.

My colleagues and I on the WUSA9 weather team will continue to keep you apprised on the latest weather updates.  Please share any snow pictures you’ve taken either as a comment to this story or on the “Wide World of Weather” Facebook page.

Washington, D.C.'s Largest Snowstorms

Red Shows Where Blizzard Warnings are in effect  (Source: NWS)

Everyone should for prepared for the historic snowstorm that will envelop the Mid-Atlantic Region this afternoon and continue through much of the weekend.  Many cities will experience one of their largest snowfalls on record.  That’s in stark contrast to the warmest December on record many eastern cities enjoyed last month.  Take a look at my column to see how much snow has to fall in Washington, D.C. for this storm to rank among the ten biggest snowstorms on record.

The Uncertainty of Forecasting Snowfall

A "High" Impact Winter Storm is on Tap  (Source: NWS)

Millions of people from the Nation’s Capital northward are poised to see the largest winter storm since “Snowmageddon” in February 2010.  Although the last two winters have had above average snowfall in the Mid-Atlantic Region, this prospective winter storm has the increasing potential of being not only high impact but could also be a historic storm.

The computer forecasting models that meteorologists use, such as the American model, “GFS” and the European model or “ECMWF” among others have shown remarkable consistency in suggesting that a coastal storm would develop on Friday.  Given the cold air that’s already in place, that would create an ideal scenario for snowfall in the Mid-Atlantic Region.  However, it’s unusual for the models to show such general agreement so far in advance, so meteorologists take notice when they do. 

These forecast models use a series of mathematical equations that rely on surface data to provide a forecast or solution.  Since surface data is limited over the ocean, it’s important to wait until a storm comes ashore so the models can incorporate more data and improve their reliability.  Since the approaching storm (that will serve as the catalyst for the anticipated coastal storm) only came ashore from the Pacific Ocean yesterday, the models should do a better job today and tomorrow of predicting how much snow is likely to occur in the Mid-Atlantic Region.

Two other key variables to monitor are the exact location of the expected coastal storm and where it tracks.  A shift in storm track of only 50 miles could make the difference between rain, mixed precipitation and snow.  If the storm tracks farther south or east, that would mean less mixed precipitation and a lower snow total for the Washington, D.C – Baltimore corridor.  A storm track farther north but offshore would result in more snow as it draws in both cold air and Atlantic and Gulf moisture – similar to the record snowstorms of December 2009 and February 2010. 

It’s important to remember that while the weather forecast models are more accurate than they used to be, they still aren’t perfect.  There is an inherent amount of uncertainty involved in forecasting winter weather.  That’s why social media is both a good and bad thing.  It helps meteorologists communicate the latest forecasts to the public and also serves as a conduit for viewers to interact with their favorite meteorologists.  The downside is that weather rumors often spread online and it’s hard for casual observers to separate legitimate information posted by scientists as opposed to sensationalized posts designed to get headlines – such as those calling for significant snow or ice accumulations a week or more in advance. 

It isn’t possible to accurately forecast snowfall amounts more than 48 to 72 hours in advance.  That’s why it’s important for people to rely upon meteorologists – such as those on the WUSA9 weather team, as well as the Capital Weather Gang.  I’ll be working with my colleagues on the WUSA9 weather team to provide the latest updates.

Washington, D.C.’s Top Ten Snowstorms (Measured at National Airport – Source: NWS)

1.  28.0” (January 27-29, 1922)

2.  20.0” (February 12-14, 1899)

3.  18.7” (February 18-19, 1979)

4.  17.8” (February 5-6, 2010)

5.  17.3” (January 7-9, 1996)

6.  16.6” (February 10-11, 1983)

7.  16.4” (December 18-19, 2009)

8.  16.4” (February 16-18, 2003)

9.  14.4” (February 15-16, 1958)

10.  14.4” (February 7, 1936)